FIELD OF THE INVENTION
The present invention concerns a process to carry out the pasteurization of alimentary mixtures and an apparatus to perform said process.
As it is known, the pasteurization of alimentary mixtures is performed by heating the mixture up to a suitable temperature for the destruction of germs (60.degree.-90.degree. C.), keeping said temperature for a given period of time, then cooling the mixture down to the preservation temperature of same.
For this purpose, in conventional pasteurizing apparatuses, the vessel containing the alimentary mixture is under conditions of thermal exchange with electric resistors, which produce the necessary calories for heating the mixture, as well as with a coil constituting the evaporator of a refrigerating circuit which carries out the subsequent cooling of said mixture.
In order to decrease the energy consumption in said machines, pasteurizing apparatuses were proposed in which the mixture heating is performed by using both the electric resistors and the heat produced by the compressor of the refrigerating circuit during the work of gas compression. To this end, the hot gas coming out of the compressor is fed directly to the coil under conditions of thermal exchange with the vessel and bypasses, through appropriate ducts, both the condenser and the lamination valve of the refrigerating circuit.
Said machines, though achieving the object of reducing energy consumption, have the drawback submitting the compressor of the refrigerating circuit to overstresses due to failed expansion and evaporation of the refrigeration fluid. In fact, during the stage of mixture heating, the refrigeration fluid does not pass through the condenser and the expansion valve and is recirculated into the compressor at a high pressure and, specially at the end of the heating stage, at a high temperature.